Out of ideas, missing - 94 Ciera 3100

[E-werd]

I am running out of ideas. The car is missing intermittently. In the beginning, it was only when it was good and warmed up. It would miss a few times, and then would be fine--and only in drive, not in neutral or park. As of today, it is missing even when cold.

What I have tried:
Changed coils
Changed cam position sensor
Changed plugs and wires (needed it, but not the problem)
Changed power steering pump (unrelated)

This may or may not be related: back in February, my lower intake gasket blew out (water in oil, oil in water). After replacing that, the SES light has been coming on. When I accelerate, the light goes out in 7-10 seconds... when I stop accelerating, the light comes back on in 7-10 seconds. Same thing happens when braking: when pressed, light goes off in 7-10 secs and comes back on after leaving up in 7-10 seconds. Ignored it, figured no big deal.

ABS light has been on, which I figured out was due to a burned out brake bulb (rear window). The light still comes on after replacing the bulbs, but only after some time. I don't figure this to be related.

When the engine isn't missing, it runs smooth as the day it rolled off the assembly line. This doesn't happen constantly. Sometimes it run good for 5-10 minutes and then starts, then is off and on. Other times it is within a minute and is off and on from there. The car does occasionally stall when these episodes happen. It is getting worse.

Before I replaced any parts, I had a code check done at Advance Auto and nothing came up... except cam position sensor, which I replaced.

Any ideas? Thanks in advance.

[SilentWing]

I would seriously suspect the ignition module, because alot of times the one thing that goes out on these cars is the ignition module which sits Under the coils and gets corroded and will cause the car to occasionally misfire and once it gets worse it'll usually drop one coil completely (IE 2 cylinders) will quit firing and it just gets worse from there. Call around to your local autozone etc some stores offer ICM testing, you'll need a 5.5mm socket to get the coils off the module. Hopefully when they test it is when it decides to act up otherwise you might get a false negative.

[85_Ciera_Rebuild]

Sometimes it run good for 5-10 minutes and then starts, then is off and on.


Checking out Ignition Module is a good idea.......but are there any power relays?

Not familiar with how relays are used (if true) in ignition circuit...if they are used, get another one and try it.

[SilentWing]

I can't remember offhand but I don't THINK there's an ICM relay on my car, I think it gets it either from the ignition switch or the PCM... IIRC it's from the ignition switch but I don't have the schematic in front of me right now.

[E-werd]

There are a bunch of relays, but I don't know what they're for... hmm. ICM makes some sense, since we were really thinking coils from the beginning, but DANG that's an expensive part.

[SilentWing]

I've got a functional one in my garage.... if you're interested i'll sell it on the cheap and can send it out tomorrow.

[85_Ciera_Rebuild]

bunch of relays...thinking coils

I've never looked at electrical schematics...but, if your fuel rail and ignition module are both "fired up" via relays...remember, shit happens, there too. Even the wires from the computer to the relays may have had been chewed upon via your local mouse cleaning its teeth on them.

[E-werd]

I've never looked at electrical schematics...but, if your fuel rail and ignition module are both "fired up" via relays...remember, shit happens, there too. Even the wires from the computer to the relays may have had been chewed upon via your local mouse cleaning its teeth on them.

I have a cat... no such small critters, their carcases all collect near the door. ;) But in all seriousness, theres no such issue of mangled, chewed, or otherwise damaged wires anywhere. I'll juggle between ICM and relays. Relays are cheaper, thats for sure. Bummer is I didn't get all these parts off the 94 Corsica 3100 before it was hauled off a couple weeks ago. :(

[Doug B.]

I'd take a look at the injectors as well, I have been down that road several times as well.. most recently a honda passport, classic symproms of a fouled plug or bad wire.. replaced those.. replaced a coil for the cylinder that wan't firing.. still no joy.. threw in the injector and it was fixed.

I only mention this because it also started out as a once in a blue moon miss, and progressively got to the point it was a full time miss. I think the actual electrics in the injector failed.. cant remember if I bothered to ohm test it as it was buried, and by the time I could test it I could replace it.

That is something you can do- narrow down what cylinder it is either by looking at the plugs or selectively unplugging ignition or injector wires till you find that one that makes no change to the miss.. I prefer interupting the injector as it doesn't stress the coil and you dont get shocked, and on the buicks its easy to reach the connector.

[E-werd]

Well, I ended up taking the ICM to Advance and, naturally, it passed the test. Not impressed, I went out to a local junkyard and grabbed an ICM off of a grand am with a 3100 (known to run before it was parted). Came home, threw it on, and went for a drive. Drove for a good 25-35 minutes, no problem whatsoever. SES light still comes on, but I am thinking at this point its just a stupid EGR code. I will know for sure in a couple of days, but this definitely looks like a success. When I replaced the coils I had success for 3 days before it started up again, so if its good Monday I am in the clear.

[turbokinetic]

Well, I ended up taking the ICM to Advance and, naturally, it passed the test. Not impressed, I went out to a local junkyard and grabbed an ICM off of a grand am with a 3100 (known to run before it was parted). Came home, threw it on, and went for a drive. Drove for a good 25-35 minutes, no problem whatsoever. SES light still comes on, but I am thinking at this point its just a stupid EGR code. I will know for sure in a couple of days, but this definitely looks like a success. When I replaced the coils I had success for 3 days before it started up again, so if its good Monday I am in the clear.

If the SES light is ON there is a code you can see, with the proper software. That is how you'll need to approach the SES light issue.

One thing to think about, it happens only when you acellerate or brake, both of which change the engine airflow characteristics. Braking uses the vacuum booster and gives the engine more air, and acellerating opens the throttle. Could you have a leaking intake pipe that is causing a false airflow reading and throwing a code for MAF sensor?

David

[E-werd]

If the SES light is ON there is a code you can see, with the proper software. That is how you'll need to approach the SES light issue.

One thing to think about, it happens only when you acellerate or brake, both of which change the engine airflow characteristics. Braking uses the vacuum booster and gives the engine more air, and acellerating opens the throttle. Could you have a leaking intake pipe that is causing a false airflow reading and throwing a code for MAF sensor?

David

I won't say no, but I'm not sure. That makes as much sense as anything else. I was thinking more towards EGR... but you're probably closer to right. For the record, pretty sure my catalytic converter is going bad, smells bad. May not be related.


Car hasn't had a problem since ICM change.